Evaluate safety and toxicity/adverse events associated with delivery of low dose whole brain irradiation in patients with early Alzheimer's dementia according to the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria.. As a secondary goal it will establish whether or not the intervention with low dose whole brain irradiation stabilizes or decreases cerebral amyloid deposits and whether these correlate with the recognized progression of Alzheimer's dementia. The investigators will also collect information from the FDG and Amyvid® PET Scans to determine if there is any correlation between neurocognitive/quality of life scores and changes in amyloid plaque size, number and location.